地层塌陷引起土体变形的阵列式三维活动门试验研究

Array three-dimensional trapdoor experimental study on soil deformation due to ground collapse

活动门试验将地层损失简化为活动门的下沉体积,可用于探讨岩溶塌陷、隧道开挖等地层损失引起的土体变形与地面沉降。目前的活动门试验以二维试验为主,对于实际的三维变形及其随地层损失增长的渐近性发展规律研究还不够深入。采用开发的12×12阵列式活动门试验装置,开展3种不同填料高度下的密实砂土三维活动门全模型和半模型试验。利用144台全阵列荷载感知系统测试得到全模型试验活动门下沉全过程的荷载变化数据,通过双轴直线滑轨–激光位移扫描装置间歇地扫描填料表面并获得全过程的表面沉降云图。对应地开展半模型试验,通过粒子图像测速(PIV)技术实时捕捉透明有机玻璃挡板后的填料内部的断面位移。利用测试得到的全阵列荷载数据得到三维活动门地基反应曲线,探讨填料剪切带随活动门下降的发展规律。揭示三维活动门试验中的填料分层沉降符合二维高斯曲线分布规律,探讨填料内部分层的沉降槽宽度与填料下沉体积的变化规律,提出三维活动门体系变形与表面沉降预测方法,试验结果可为相关工程中的土体变形与地表沉降预测提供参考。

In trapdoor tests,ground loss is typically simplified as the settlement volume of the trapdoor.Trapdoor tests are commonly used to study the soil deformation and surface settlement induced by the karst collapse and tunnel excavation.However,the current trapdoor tests are mostly in 2D conditions.Future investigation is needed to understand the progressive development of soil deformation with ground loss in 3D conditions.In this study,dense sand half and full 3D trapdoor tests were conducted using a 12×12 array trapdoor test device with 3 different fill heights.144 load sensors were used to monitor loading variations during trapdoor settlement in full tests.Laser displacement transducers,which could move on the biaxial linear tracks were used to measure the deformation of the fill surface and later to calculate the surface settlement contour.Laser displacement transducers measured fill surface deformation and calculated the surface settlement contour.The half trapdoor tests were conducted to corresponding the full trapdoor tests and the particle image velocimetry(PIV)technique captured the cross-section deformation behind the plexiglass plate.In this study,the ground reaction curve was calculated based on full trapdoor test results,and the development mechanism of the shear band with trapdoor settlement was evaluated.This study revealed that settlement at different layers from 3D trapdoor tests well matched the 2D Gaussian distribution curve and discussed the relationship between the settlement width and the settlement volume.Additionally,this study proposed a method to predict the surface settlement and ground deformation in 3D trapdoor test conditions.The results of this study can provide guidance for soil deformation and surface settlement in real projects.